The present invention relates to a mobile telephone, especially a voice recording device thereof.
As a voice recording device of a conventional mobile telephone, for example, the Japanese Patent Laid-Open Publication No. HEI 2-78058 discloses the voice recording device which provides an analog/digital converter for converting an analog voice signal to a digital voice signal at a fixed sampling frequency, a memory means for memorizing voice data converted analog to digital by the sampling frequency and a digital/analog converter for converting signals read out from this memory means digital to analog. Moreover, the voice recording device provides a time measuring means for measuring recording time and a compression rate controller for controlling to increase the compression rate of the voice signals responding to the increase of the recording time measuring by this time measuring means. In this example, this voice recording device has constitution having variable recording time by changing the sampling rate.
At the mobile telephone which is usable for plural digital mobile telephone systems, it is necessary that the mobile telephone has plural voice encoder/decoder i.e. voice codecs having voice compression systems stipulated by the systems respectively. For example, at the case of the mobile telephone which is usable for both PDC and PHS systems, at this , PDC system is the Japanese digital mobile telephone system, it is necessary that the mobile telephone provides both voice codecs named V-SELP and PSI-CELP systems adopted by PDC system and a voice codec named ADPCM system adopted by PHS, or switches to either system by computer software.
Moreover, at the conventional digital mobile telephone system, and at a telephone answering state or a busy state, the voice recording device is utilized widely to record a message from callers. To meet this, for example at PDC, by applying voice compression of V-SELP and PSI-CELP being standard voice codecs, a storing means for storing voice data encoded by these voice codecs in a memory is used, at this, encoded data means compressed data. In this case, a voice encoding (compressing) device only for the voice recording is not needed, the construction of the device is simplized.
However, in the case that the voice recording is implemented by utilizing the voice codec stipulated by the mobile telephone system at the conventional technology, there are following problems.
The encoding rate (data compression rate) of the voice codec of PDC is different from that of PHS, therefore at the mobile telephone usable for plural digital mobile telephone systems, such as a mobile telephone usable for both PDC/PHS, even at the memory has the same storage capacity, the recording time and numbers are different between PDC and PHS. For example, even providing the memory capable of recording 40 seconds at V-SELP of PDC, ADPCM of PHS can record for only about 8 seconds being about ⅕ of PDC. Therefore, even the storage capacity is excess for PDC, the memory enough to record at PHS should be provided, then there is a disadvantage for cost.
At the conventional technology, both the voice codec needed for the system itself and the codec for voice recording are required to be provided, therefore by using additionally a voice compression device only for recording that is not the voice codec using at the radio system, at the above mentioned case usable for both PDC/PHS, the recording time is not different between the different systems. However, in this case the circuit size becomes large.
Generally, the relation between the compression rate and the voice quality is a tradeoff at the conventional technology, however it is convenient for user to be able to choose the voice quality or the recording time as priority, therefore at the mobile telephone usable for plural systems, such as usable for both PDC and PHS, the voice quality is different among systems. For example, in the case using the same voice encoder for both PDC and PHS, especially at adjusting to the voice encoder of the bad voice quality system, the advantage of PHS i.e. the good voice quality is not possible to be kept.
It is therefore an object of the present invention to provide a mobile telephone whose circuit is able to be simplified with small added circuit, at putting a voice recording function to the mobile telephone, and provides a mobile telephone in which data encoded by ADPCM of PHS is able to be converted to the data encoded by PSI-CELP or V-SELP of PDC and in case of that a user wants to store more voice data, the voice data of PHS is further compressed and is able to be stored, and provides a mobile telephone in which the voice recording time is able to be increased and a user is able to choose the voice quality or the recording time as priority.
According to a first aspect of the present invention, to solve the above mentioned problems, in a mobile telephone which has switchable plural voice encoding systems stipulated corresponding to communication systems, the present invention provides a mobile telephone, having an encoding/decoding means for encoding and decoding voice of caller or user corresponding to a first voice encoding system in said plural voice encoding systems stipulated by said communication systems, a voice data storing means for storing the encoded voice data, a voice data decoding and playback means for decoding and playback said stored voice data in said voice data storing means at the arbitrary time, a voice data decoding means for producing decoded data decoding said voice data stored by said first voice encoding system at the arbitrary time, a decoded data storing means for storing said decoded voice data temporarily and a data compression means for compressing the data by storing in said voice data storing means the re-encoded data by a second voice encoding system in said plural voice encoding systems.
According to a second aspect of the present invention, the mobile telephone provides a data compression selection means in which the user himself can select whether the voice data stored in said voice data storing means are compressed or not arbitrarily.
According to a third aspect of the present invention, the mobile telephone provides a re-encoding means in which during call the voice of caller is decoded and played back from a speaker, at the same time, the voice is re-encoded in another voice encoding mode stipulated by the system, wherein said voice data storing means is operated as a memory means memorizing the reencoded voice data.
According to a fourth aspect of the present invention, in the mobile telephone, said data compression means utilizes the voice encoding/decoding means stipulated by said communication systems for voice recording and converts the voice data stored by the plural voice encoding systems to the highest data compression rate encoding system and makes the long recording time possible.
According to a fifth aspect of the present invention, in the mobile telephone, said decoding and playback means and said data compression means include a voice codec section providing decoders and encoders corresponding to said plural voice encoding systems and said voice codec section is constituted of hardware or software.
According to a sixth aspect of the present invention, in the mobile telephone, said data compression means decodes the voice data by ADPCM system and encodes by PSI-CELP system and stores in said voice data storing means.